1. Technical Field of the Invention
The present invention relates generally to a hermetic compressor, and more particularly to an improved structure of a hermetic compressor for compressing refrigerant used in a refrigeration system such as an electric refrigerator.
2. Background Art
Various compressors for use in refrigeration systems are known in the art. In recent years, high energy efficiency and noiseless compressors are sought.
U.S. Pat. No. 4,723,896 discloses a conventional hermetic compressor wherein the size of an outlet port formed in a valve plate is decreased for promoting the efficiency of compression. This compressor includes a reed valve arranged on the outlet port of the valve plate, a support spring, a valve stopper, and a holding spring which are mounted on the reed valve to form a preassembly. The mounting of the reed valve, the supporting spring and the valve stopper in a compressor casing is accomplished by pressing the holding spring when a cylinder head is installed on a cylinder block.
The above compressor, however, encounters a drawback in that it is difficult to check whether the reed valve and a spring urging the reed valve to a closed state have been arranged properly or not.
Japanese Patent First Publication No. 04-506082 teaches a hermetic compressor designed for improving the energy efficiency. FIG. 11 shows this prior art compressor. A valve plate assembly 300 includes an inlet reed valve 22, a valve plate 20, a pair of outlet reeds 34, a reed spring 40, a stopper 42, and rivets 48.
The valve plate 20 has formed therein an inlet port 28 and two outlet ports 29. The inlet port 28 communicates with a compression chamber of a compressor unit for introducing refrigerant gas thereinto. The outlet ports 29 discharge the refrigerant gas compressed in the compression chamber to an outlet plenum formed in a cylinder head.
The inlet reed valve 22 is made of a fiat plate and forms an inlet valve 30 and four mounting holes 31 in its comers in alignment with mounting holes 51 formed in the valve plate 20.
An elongated recessed portion 32 is formed in the valve plate 20 which has formed therein the outlet ports 29. Annular valve seas 33 are formed coaxially with the outlet ports 29. The height of the valve seats 33 are set smaller than the depth of the recessed portion 32.
Each outlet reed valve 34 includes a sealing portion 35 and a pair of extensions 36. The recessed portion 82 has formed on its inner side walls two pairs of protrusions 38 inwardly oriented to each other to define end housings between the protrusions 38 and end walls 37, respectively. The extensions 36 of each outlet reed valve 34 are fitted into the end housing 38. A bottom of each end housing rises to form a stepped portion 39 which has substantially the same height as that of the valve seats 33. The outlet reed valves 34 are mounted in the recessed portion 32 in contact with the stepped portions 39 and the valve seats 33.
The reed spring 40 Is formed with a strip plate which has both ends 41 bent at a given angle and has the length shorter than an interval between the end walls 37 of the recessed portion 32. The reed spring 40 is mounted in the recessed portion 32 through the outlet reed valves 34 with both ends 41 thereof pressing the outlet reed valves 34.
The stopper 42 includes a pair of stepped portions 44 and a mounting portion 45. The mounting portion 45 secures the stopper 42 on the valve plate 20 using the rivets 48. The stepped portions 44 are partly inserted into the recessed portion 32 so that they press bent portions 43 of the reed spring 40 under a given pressure. These arrangements provides high compression efficiency. The provision of the two outlet ports 29 prevents overcompression loss from being increased.
The above prior art compressor, however, has suffered from the drawback in that the two outlet ports 29 cause operational noise to be increased. In addition, when refrigerant gas HFC-134a is used in place of CFC-12, heavier noise is found to be produced.